The present application is a continuation proposal for an ongoing longitudinal study of the effects of exposure to conflict and violence on the mental health and behavior of Palestinian and Israeli youth. Three cohorts of youth (originally ages 8, 11, and 14) have been assessed three times at one-year intervals. Analyses of the data collected through June 2010 have shown that exposure to ethnic-political and war violence is related to subsequent post-traumatic stress symptoms and aggression directed at peers. The goals of the current proposal are to continue analyses with the three waves of data collected by June 2010 and to collect one more wave of data with a more intense focus on the older cohort as they now reach adulthood (age 20 in 2013) in order to examine effects of cumulative exposure to violence on clinical syndromes, substance use, antisocial and aggressive behavior, and endorsement of politically-motivated violence. Additionally, we will examine age-relevant potential protective factors that we did not previously assess for this older cohort (e.g., civic engagement, employment, constructive activities, political activism, and post traumatic growth). Our focus on the older cohort is motivated by the recognition that early adulthood is a period in which new opportunities and experiences present challenges to adjustment and when age-salient protective factors may moderate the impact of persistent exposure to violence. However, for all age cohorts, we propose to extend our assessment of mental health outcomes and extend our examination of the role of emotional reactivity in response to ethnic-political violence exposure by collecting bio-markers (e.g., cortisol) and assessing skin conductance in response to viewing a video depicting interpersonal violence. This will allow us to test key theoretical propositions concerning mediating cognitive and emotional processes that might account for the long-term effects of violence exposure and distinguish between those highly exposed youth who display more externalizing problems and those who display more internalizing problems.